12.1 Behavior
of Light
I. Light and Matter
•
•
Vision depends on amount of light and color
We see reflected light
A. Opaque, Transparent, and Translucent
1. Objects can absorb, reflect, or transmit light.
a. Opaque - absorbs and reflects light
b. translucent – transmits some, reflects and
absorbs some
c.
Transparent – transmits light
II. Reflection of Light
1. Light reflects, hits the
mirror, and back to
your eye..
2. The angle of
incidence equals the
angle of reflection.
A. Regular and Diffuse Reflection
1. Regular reflection - off a smooth surface such as a
mirror
2. Uneven surfaces reflects light in many directions
● This is called diffuse reflection
3. Some surfaces look smooth but
cause diffuse reflection.
III. Refraction of Light
• The speed of light changes as it
passes through objects.
• The light appears to bend.
A. The Index of Refraction
1. Amount of bending depends on speed
through materials
2. Bigger I.R. will produce more bend.
3.
Index of refraction –
How the speed of light is
reduced when it passes
through different
mediums.
a. Larger IR, the
more light is
slowed down.
B. Prisms
1.
2.
3.
4.
Refract light twice – entering and leaving
Longer wavelengths, smaller I.R.
Red is longest, so is bent the least.
Separates colors by wavelength
C. Rainbows
1. Drops act like prisms.
2. Refraction causes colors to separate
3. ROY G BIV
D. Mirage
1. Mirage - an image produced by the refraction
of light through air layers of different densities.
a. Air at ground is warmer than the air above it.
b. Light travels slower in cooler air so they
refract.
https://www.youtube.com/watch?v=4fyz5aNPAno
Section Check
Question 1
What is the law of reflection?
Section Check
Answer
According to the law of reflection, the angle at which a
light wave strikes a surface is the same as the angle
at which it is reflected.
Section Check
Question 2
What happens to light waves that strike an object?
Answer
Light waves that strike objects can be absorbed, reflected,
or transmitted.
Section Check
Question 3
What is the difference between refraction and
reflection?
Section Check
Answer
Refraction occurs if a light wave changes speed in
moving from one material to another. Reflection
occurs when light waves bounce off a surface.